Drilling tool

ABSTRACT

The invention relates to a drilling tool for drilling soft and fragmented rock. The drilling tool disclosed in the invention comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at its end, a converging part through which conduits pass for rinsing medium.

BACKGROUND OF THE INVENTION

The invention relates to a drilling tool for drilling soft and fragmented rock.

Presently, when soft and fragmented rock is drilled, typically either a grooved guide tube or a separate protective tube is used, which is either left in the hole or withdrawn from the hole after the drilling. The intention is to prevent the material surrounding the hole from caving in to enable the withdrawal of the drill bit from the hole as the last action.

A prior art drawback is that when a grooved guide tube is used, the grooved portions of the tube may break the wall of the hole, which makes the hole cave in regardless of the intention to the contrary. Furthermore, if a separate protective tube is used, extra equipment is required for installing and disassembling the protective tubes.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a drilling tool for preventing better than previously the caving in of the hole walls when fragmented or soft material is being drilled.

The drilling tool of the invention is characterized in that it comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at least at the end intended to be positioned towards the rock drill, a part converging towards the axis of the drill rod, and that it comprises, for rinsing medium, through-going conduits that terminate in said converging part.

It is an essential idea of the invention that the drilling tool is a part that has a smooth outer surface, is positioned symmetrically relative to the middle axis of the drill rod and comprises converging ends in such a manner that during the rotation of the drill rod it penetrates through the material that tends to cave in and simultaneously compresses and grinds the material tightly against the wall of the drill hole.

The tool of the invention is further characterized in that it comprises through-going longitudinal conduits, through which the rinsing medium is allowed to flow away from the drill hole.

An advantage of the invention is that during the drilling of soft or fragmented material, the drill hole can be kept open, as the tool compresses the detaching material tightly into the wall of the drill hole.

A further advantage of the invention is that since the flow of rinsing medium is arranged through the drilling tool, and not along the grooves on its outer surface, the flow of rinsing medium does not corrode or detach material from the wall of the drill hole very easily, and thus does not cause cave-ins very easily in a ready-made hole.

A still further advantage of the invention is that if for some reason the drill hole caves in, it can be opened quite easily by means of the drilling tool.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described in more detail in the attached drawings, wherein

FIG. 1 schematically shows an embodiment of a drilling tool installed in a drill rod,

FIG. 2 schematically shows an embodiment of a drilling tool seen from above,

FIG. 3 schematically shows the drilling tool shown in FIG. 2 in the longitudinal direction in section along line A-A,

FIG. 4 shows another embodiment of the tool disclosed in the invention, and

FIG. 5 shows still another embodiment of the tool disclosed in the invention.

In the figures, some embodiments of the invention are shown in a simplified manner for the sake of clarity. In the figures, like parts are denoted with the same reference numerals.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

FIG. 1 shows a drilling tool of the invention installed in a drill rod. It shows a short drill rod 1, one end of which comprises an external thread 2 for fastening a drill bit, the other end comprising an internal thread 3 for fastening a second drill rod. A drilling tool 4 is fastened onto the drill rod 1. In this embodiment, the drilling tool 4 is installed in a separate short part of the drill rod intended to be installed between a normal drill bit and a drill rod of a normal length. Furthermore, each end of the drilling tool 4 is provided with a converging part 4 a, which is connected to the drill rod at each end thereof and, correspondingly, to the middle part of the drilling tool in a rounded manner in a manner generating a smooth, even surface. The purpose of this is to make the shape of the drilling tool 4, when it hits the wall of a caved-in drill hole or a drill hole tending to cave in, compress the detaching or detached material against the wall of the drill hole, its cylindrical part, when the drill rod is rotating, as if compressing the wall firmly and tightly together. FIG. 1 further shows openings 5 at the converging part 4 a at both ends of the drilling tool 4. The openings 5 are interconnected by means of a conduit described later in connection with FIG. 3, allowing rinsing medium to flow between the ends of the drilling tool 4 without the rinsing medium having to flow from between the outer surface of the drilling tool and the surface of the hole. Typically, such a rinsing medium flow may cause caving in of the walls of a hole.

FIG. 2 schematically shows a drilling tool seen from the end. The cross section of the drilling tool 4 is substantially cylindrical and the tool has a smooth surface. Its diameter is dimensioned in a manner making it slightly smaller than the outer diameter of the drill bit intended to be used therewith. The reason for this is to allow the tool to pass through a hole made by the drill bit in a hole drilled in a potentially hard rock. It also shows how a plurality of conduits 5 a lead through the drilling tool 4 for allowing rinsing medium to flow out of the drill hole. FIG. 2 also shows a conduit 1 a in the middle of the drill rod 1, along which conduit the rinsing medium flows to the drill bit and further through conduits therein to the drill hole for transporting drilling residue out of the drill hole.

FIG. 3 schematically shows the drilling tool according to FIG. 2 in the longitudinal direction in section along line A-A. As it shows, the openings 5 are at the ends of the conduit 5 a inside the drilling tool. A suitable number of such conduits, e.g. 6 or less or more, may be positioned around the axis of the drilling tool. It is essential that the number and the common cross-sectional area of the openings are sufficient for the outflow of the rinsing medium and the material transported therewith. The cross section of the conduits passing through the drilling tool may be, not only round, but also of another shape, such as angular, oval, etc. Similarly, the edges of the opening may be inclined inwards, allowing them to push the material outwards from the openings when hitting it.

FIG. 4 schematically shows another embodiment of drilling tool. Here, the drilling tool is arranged at one end of a drill rod 1 of a conventional length, close to the external thread 2 such that it is positioned almost immediately after the drill bit, when the drill bit is fastened to the drill rod 1. This being so, the control and operation of the drilling rig are as in normal drilling, and no separate short drilling for using exclusively the drilling tool is required at the beginning of the drilling.

FIG. 5 schematically shows still another embodiment of a drilling tool. Here, the drilling tool is composed as an entity integrated into the drill bit 6. Here, the conduits for removing rinsing medium and drilling residue naturally pass straight through the drill bit and the tool part.

In the above description and in the drawings, the invention is only described by way of example and in no way restricted thereto. In some cases, the characteristics disclosed in the present application may be utilized as such, irrespective of other characteristics. On the other hand, when desired, the characteristics disclosed in the present application may be combined for generating different combinations. The drilling tool may be fastened onto the drill rod in a plurality of manners known per se. For example, the drilling tool may be pushed onto the drill rod and then welded thereto at its ends, followed by finishing of the surface suitably smooth. Alternatively, the drilling tool, preferably comprising only a short drill rod, may be directly machined as a solid entity, for example. Other manners of manufacture and fastening are also usable.

The drawings and the related description are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims. 

1. A drilling tool for drilling soft and fragmented rock, which tool comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at least at the end intended to be positioned towards the rock drill, a part converging towards the axis of the drill rod, and that the tool comprises, for rinsing medium, through-going conduits that terminate in said converging part, wherein the largest outer diameter of the tool is dimensioned smaller than the outer diameter of the drill bit intended to be used therewith.
 2. A drilling tool as claimed in claim 1, wherein the drilling tool is a part separate from the drill bit and both of its ends are provided with a part that converges towards the axis of the drill rod and that the conduits for the rinsing medium lead from the converging part to an opposite, converging part.
 3. A drilling tool as claimed in claim 2, wherein the middle part of the drilling tool is substantially cylindrical and that one end of the drill rod is provided with an external thread, the other being provided similarly with an internal thread for connecting the drill bit and the drill rods, respectively, thereto.
 4. A drilling tool as claimed in claim 2, wherein the drilling tool is installed at the end on the side of the external thread of the drill rod of a normal length.
 5. A drilling tool as claimed in claim 1, wherein the drilling tool is a part integrated into the drill bit. 